A typical disk drive storage system includes one or more magnetic disks which are mounted for co-rotation on a hub or spindle. A typical disk drive also includes a transducer supported by a hydrodynamic bearing which flies above each magnetic disk. The transducer and the hydrodynamic bearing are sometimes collectively referred to as a data head or a product head. A drive controller is conventionally used for controlling the disk drive based on commands received from a host system. The drive controller controls the disk drive to retrieve information from the magnetic disks and to store information on the magnetic disks. An electromechanical actuator operates within a negative feedback, closed-loop servo system to move the data head radially or linearly over the disk surface for track seek operations and holds the transducer directly above a desired track or cylinder on the disk surface for track following operations.
Typically the magnetic disks 2 also comprise servo sectors 18 which are recorded at a regular interval and interleaved with the data sectors 12, as shown in FIG. 1. A servo sector, as shown in FIG. 2, typically comprises a preamble 20 and sync mark 22 for synchronizing to the servo sector; a servo data field 24 comprising coarse position information, such as a Gray coded track address, used to determine the radial location of the head with respect to the plurality of tracks; and a plurality of servo bursts 26 recorded at precise intervals and offsets from the track centerlines which provide fine head position information. When writing or reading data, a servo controller performs a “seek” operation to position the head over a desired track; as the head traverses radially over the recording surface, the Gray coded track addresses in the servo data field 24 provide coarse position information for the head with respect to the current and target track. When the head reaches the target track, the servo controller performs a tracking operation wherein the servo bursts 26 provide fine position information used to maintain the head over the centerline of the track as the digital data is being written to or read from the recording surface.
Every disk in every drive will have errors. Prior to shipping disk drives, manufacturers test each drive using a write then read process to determine whether the number of errors is below a predetermined threshold. If the number of errors is above the threshold, the drive fails. However, it is not known at this point whether the problem lies with the disk, the head, or other hardware. What is therefore needed is a method for efficiently determining whether the problem on a failed drive is disk related or head related.